The 'graininess' in the energy content of light is reported in experiments ranging from the blackbody spectrum and photo-electric
effect to revivals in the Jaynes-Cummings model. Laser shot noise and antibunching of correlations in resonance fluorescence signify
a departure from continuous wave behavior for light. Such phenomena underlie the unique sense in which a photon is regarded as an
indivisible particle, experimentally tied to the fact that a beam splitter does not split a single photon of a two-photon pair. We
consider three arguments for indivisibility - quantization of energy, particle-like fluctuations, and which-way measurements. We
argue that in each case, photon indivisibility is an inference based on energy conserving interactions where the detection mechanism
involves countable electrons subject to space and bandwidth limitations. The indivisibility of the photon thus remains an open
question, and one that we can use to probe the foundations of quantum electrodynamics.
We review and sharpen the concept of a photon wave function based on the quantum theory of light. We argue that a point-like atom serves as the archetype for both the creation and detection of photons. Spontaneous emission from atoms provides a spatially localized source of photon states that serves as a natural wave packet basis for quantum states of light. Photodetection theory allows us to give operational meaning to the photon wave function which, for single photons, is analogous to the electric field in classical wave optics. Entanglement between photons, and the uniquely quantum phenomena that result from it, are exemplified by two-photon wave functions.
Conference Committee Involvement (2)
The Nature of Light: What are Photons? III
3 August 2009 | San Diego, California, United States
The Nature of Light: What are photons?
26 August 2007 | San Diego, California, United States